The present invention generally relates to releasable locking devices and, more particularly, to a releasable locking device for frictionally engaging a bar member or the like.
Among the many types of releasable locking devices are internal twist locks for telescoping members employing an eccentric collar. Such internal twist locks are old in the art and, more recently, improvements in locking ability have been made by replacing the eccentric collar with cam surfaces such as those typically shown in Nielsen, Jr. U.S. Pat. No. 3,515,418 and Davidson U.S. Pat. No. 2,991,096. With the internal twist locking devices of this type, the telescoping members themselves are utilized as the acting and reacting members as locking and unlocking occurs.
Among variations of internal twist locking devices are those typically shown in Hume U.S. Pat. No. 2,546,157 and Peterson et al. U.S. Pat. No. 2,871,044. These devices utilize an external rotatable collar associated with one of a pair of telescoping members where the collar cooperates with the other telescoping member as the acting and reacting members. In typical fashion, the collar can be rotated in one direction to lock the telescoping members in one position and can be rotated in the other direction to unlock the telescoping members for movement to another position.
Still another form of releasable locking device has been proposed in Pinto et al. U.S. Pat. No. 4,154,545. This device utilizes two external collars as the acting and reacting means, but it also employs taper actuated collet type locking means engaged by axial movement of the collars caused by the spreading action of two face cams on the collars. Clearly, the device disclosed in Pinto et al. U.S. Pat. No. 4,154,545 has a number of disadvantages.
In particular, the Pinto et al. device provides no means for releasing the taper actuated collet once the collars are in a locked position. Specifically, a low taper will provide high collet gripping power but will be self-locking, i.e., the low taper will render it difficult to move the collars from a locked to an unlocked position. On the other hand, if the tapers are large enough to be self-releasing, the gripping power of the collet will be much lower.
Accordingly, it has remained to provide an entirely satisfactory releasable locking device where a telescoping member need not be twisted to produce the locking condition. It has also remained to provide a releasable locking device which can be moved along a bar member and locked in any position and wherein double locking occurs to thereby provide a safety provision not found in locking collars now on the market. Further, it has remained to provide an entirely satisfactory releasable locking device capable of economical manufacture and assembly for a multitude of applications.